1. Field of the Invention
The present invention provides methods of forming permeable sand screens in well bores to prevent sand from flowing into the well bore with produced hydrocarbons and other fluids.
2. Description of the Prior Art
Oil, gas and water producing wells are often completed in unconsolidated subterranean formations containing loose or incompetent sand which flows into the well bores with produced fluids. The presence of the sand in the produced fluids rapidly erodes metal tubular goods and other production equipment which often substantially increases the costs of operating the wells.
Gravel packs have heretofore been utilized in wells to prevent the production of sand. Such gravel packs are comprised of a pack of gravel such as graded sand which is placed in the annulus between a perforated or slotted liner or screen and the walls of a well bore in the fluid producing zone. The resulting structure provides a barrier to migrating sand from the producing zone while allowing the flow of produced fluids. Gravel packs have successfully prevented the production of sand with formation fluids, but they often fail and require replacement. For example, gravel packs frequently fail due to the deterioration of the perforated or slotted liner or screen as a result of corrosion or the like. The initial installation of a gravel pack adds considerable expense to the cost of completing a well and the removal and replacement of a failed gravel pack is even more costly.
Thus, there are continuing needs for improved methods of preventing the production of formation sand, fines and the like with produced subterranean formation fluids.
The present invention provides improved methods of forming permeable sand screens in long, open hole well bores within fluid producing zones which meet the needs described above and overcome the deficiencies of the prior art. The methods of the invention are basically comprised of the following steps. A perforated pipe containing a plurality of openings around and along the length thereof is placed in an open hole well bore adjacent to a fluid producing zone. The perforated pipe is of a size such that its external diameter is smaller than the diameter of the open hole well bore. A hardenable composition is provided which after being placed in a desired location cures into a hard permeable mass. The hardenable composition is placed in the well bore adjacent to the fluid producing zone within the interior of the perforated pipe therein, between the perforated pipe and the walls of the open hole well bore and within voids or fractures in the producing zone. Thereafter, the hardenable composition is caused to cure into a hard permeable mass, and the part of the hard permeable mass within the interior of the perforated pipe is drilled out of the pipe.
An alternate embodiment of the present invention is comprised of the following steps. A perforated outer pipe containing groups of openings around the periphery thereof spaced from each other along the length of the pipe and having a smaller drillable perforated inner pipe attached within the outer pipe which includes groups of openings that are longitudinally offset from the groups of openings in the outer pipe is provided. The perforated outer pipe containing the drillable perforated inner pipe is placed in the open hole well bore adjacent to the fluid producing zone. The perforated outer pipe has an external diameter smaller than the diameter of the open hole well bore. A hardenable composition is provided which after being placed in a desired location cures into a hard permeable mass. The hardenable composition is placed in the well bore adjacent to the fluid producing zone within the interior of the drillable perforated inner pipe, between the drillable perforated inner pipe and the perforated outer pipe, between the perforated outer pipe and the walls of the well bore and within voids or fractures in the producing zone. Thereafter, the hardenable composition is caused to cure into a hard permeable mass, and the part of the hard permeable mass within the interior of the perforated outer pipe along with the drillable perforated inner pipe and the hard permeable mass within it are drilled out.
The hardenable composition utilized can be a hydraulic cement composition which includes particles, beads or fibers which are soluble in acids or liquid hydrocarbons. Upon hardening, the cement mass formed is contacted with an acid or a liquid hydrocarbon to thereby dissolve the particles, beads or fibers in the cement composition and permeate it whereby produced hydrocarbons can flow through the permeated cement composition, but loose or incompetent sands cannot. A hydraulic cement composition which includes cross-linked aqueous gel particles containing internal temperature activated breakers which cause the gel particles to break into a liquid can also be utilized as can a hardenable resin coated particulate material which cures into a hard permeable mass.
It is, therefore, a general object of the present invention to provide improved methods of forming permeable sand screens in well bores.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.